The present invention relates generally to multiple digital data storage device systems and, more particularly, to at least two high capacity disk drive data storage devices having a specified physical size mounted in a larger standardized form factor package forming a single unit.
One of the principle components of a computer system is a place to store data. Typically computer systems employ a number of storage means to store data for use by a computer system. For example, a computer system can store data in a peripheral storage device referred to as a disk drive or direct access storage device (DASD).
A disk drive or DASD includes one or more disks which appear similar to records utilized with a record player or compact disks (CD) which are utilized with a CD player. The disks are stacked on a spindle for rotary motion in parallel planes, much like records. In a disk drive, however, the disks are mounted to the spindle and spaced apart so that the separate disks do not touch each other.
Such data storage devices employing rotating magnetic or optical media disks are well-known for high capacity, low cost storage of data. Such disks typically have a multiplicity of concentric data track locations formed on one or both surfaces, each capable of storing useful information. The information stored in each track is accessed by a transducer head which is moved among the tracks during track seeking operations and which is maintained in alignment with the track during read only and/or read/write track following operations of the device. Typically one or more transducer heads are provided for each data storage surface. The electro-mechanical assembly for rotation of the disk relative to the head and for moving the head radially relative to the disk surface for track accessing purposes is referred to as the head and disk assembly (HDA). A control mechanism is provided in order to maintain the head within the boundaries of each data track, and may take the form of detents provided by a stepping motor, or by a continuously positionable actuator operating within a closed loop servo, or a time-sampled servo. Additionally, an interface device is required for connection of the HDA to a controller and for communication between the disk drive and the computer system. Typically, a standardized interface is utilized, for example, the Small Computer Synchronous Interface (SCSI).
Today's technology relating to data storage is marked by continuing trends towards standardization and towards increased storage capacity, reduced data storage device weight and size, and reduced power consumption. Standardization in size, referred to as form factor, and in interface compatibility is being pursued by manufacturers of both desktop systems such as personal computer (PC) and workstation systems and larger computing systems. Thus, disk drives having differing capabilities and capacities provided in standard form factors and plug-in configurations by several different manufacturers may be used interchangeably in different PC's, for example, in standardized plug-in slots provided by the PC manufacturers.
Increasing system storage capacity while reducing disk drive size requires careful balancing of the reduction of the area of the storage medium, i.e., the area of the disk surface, against the corresponding reduction in storage capacity. Typically, the tradeoff is to increase the number of disks per spindle and/or increase the number of disk drives. On a iarge scale, large numbers of relatively small disk drives are mounted in drawers to provide high storage capacity while taking advantage of common power supplies and cooling facilities, for example, to achieve an overall reduction in power requirements. However, for a PC, for example, a user is limited to adding individual disk drives in the standard form factor slots provided by the PC manufacturer or by adding relatively expensive stand-alone units.